Influence of radiant exposure on degree of conversion,water sorption and solubility of self-etch adhesives

The purpose of this study was to investigate the influence of the radiant exposure on the degree of C=C conversion (DC), water sorption (WS), and solubility (S) of the Clearfil SE Bond (CSE) and Filtek LS (LS) self-etch adhesive systems. The primer of the LS (LSP), and bond agents of the CSE (CSEB) and LS (LSB) were tested. Specimens were light-cured using a light-emitting diode (LED) at different radiant exposures (6.1, 12.2, 13.9, and 27.8 J/cm²). DC (n=10) was measured using Fourier-transform infrared spectroscopy (FT-IR). WS and S were determined according to ISO 4049. Data were subjected to two-way ANOVA and Tukey's test at pre-set alpha of 0.05. The highest DC was exhibited by LSP, followed by CSEB and LSB, all with statistical difference (p<0.001). The DC was increased with higher radiant exposure and extended light-curing time (p<0.001). LSB and CSEB showed the lower WS followed by LSP, all with statistical difference (p<0.001). CSEB and LSB presented no significance difference on the S values (p>0.05) and were lower than LSP (p≤0.05). The WS and S were not influenced by the different radiant exposures evaluated (p=0.9548 and p>0.05, respectively). The monomer conversion is related to improvement on the mechanical properties of resinous material, but these properties also depend on the polymer network structure formed.     

The electronic structure of oxide-supported tungsten oxide catalysts as studied by UV spectroscopy

The UV spectra of tungsten oxide catalysts supported on alumina, titania and zirconia, and on titania–alumina and titania–zirconia mixed oxides are reported and discussed. Evidence is provided for the different electronic structure of supports and catalysts, which could affect the behavior of the tungsten oxide centres in the different cases. On alumina, tungsten oxide centres are “isolated” by the insulating support, while on titania-based materials they are likely in electronic contact with each other and with Ti centres through the support conduction band. In the case of WOx2013;ZrO₂, the 5d levels of tungsten ions fall just below of the lower energy limit of the support conduction band. This revised version was published online in July 2006 with corrections to the Cover Date.     

FTIR study of thermal cyclization processes in the synthesis of polyetherimidazopyrrolones

An FTIR method was used to investigate the thermal cyclization process in synthesis of polyetherimidazopyrrolones from dietherdianhydrides and 3,3′-diaminobenzidine. It was concluded that the highest degree of cyclization to imidazopyrrolone structure is observed in the case of polymer with bisphenol A group having electron-donating character after dynamic heating, though for the all polyether-imides investigated even at 320°C cyclization are not complete.     

不对称五氮齿镉和铟大环配合物的合成及其光物理性质研究

不对称五氮齿镉和铟大环配合物的合成及其光物理性质研究郭丰启孙文芳谢洁王夺元（中国科学院感光化学研究所,北京１００１０１）关键词不对称五氮齿金属配合物,电子吸收光谱,荧光１９９７年９月３日收到初稿,１９９７年１２月３０日收到修改稿．国家自然科学...     

The kinetic behaviour of ion injection in WO3 based films produced by sputter and sol–gel deposition: Part II. Diffusion coefficients

The use of AC impedance spectroscopy for kinetic study of the ion intercalation into WO₃ films is reviewed, and methods for extracting the diffusion coefficient of the ion diffusion process from AC impedance spectroscopy data are described. These are applied to several different electrochromic thin films, all based on tungsten oxide, and the electrochromic performance is correlated with the diffusion coefficient. The results are also compared with results of a previous paper which concentrated on modelling the voltage response of films coloured and bleached using constant current charge injection techniques. Several examples of non-ideal behaviour of the impedance spectra are observed, including depressed semicircles and evidence of two semicircles. A full discussion of these effects is given in a following paper.     

The role of ion and solvent transport during the redox process of conducting polymers

The understanding of the redox behavior of conducting polymers is essential for a successful application of these so-called synthetic metals as functional coatings. The redox process involves the exchange of ions and solvent molecules. This so called doping/dedoping process involves changes of the mechanical and the electronic structure of the polymer. This paper discusses investigations at poly(3,4-ethylenedioxythiophene (PEDOT) and poly(pyrrole) (Ppy) by the electrochemical quartz crystal microbalance (EQCM) technique and electrochemical impedance spectroscopy (EIS). In the case of PEDOT a determination of the anion and the solvent fluxes was possible, and it was found that most anions replace solvent molecules upon their incorporation. The doping/dedoping mechanism of Ppy is more complicated. Here, the first redox cycles are characterized by a complex interplay of cation, anion and solvent fluxes with irreversible changes of the polymer structure. However, in combination with EIS new insights of the ion and solvent exchange and its influence on the electronic properties can be achieved.     

基于改进型序阻抗原理的变压器保护方案

基于序阻抗原理的变压器保护方案利用变压器发生区内外故障时,变压器两侧正负序阻抗所在象限的不同,来有效识别变压器区内外故障,文中在此方案基础上,改进了象平面区域的划分,补充了励磁涌流识别判据,并讨论了在特殊情况下所应采取的措施.在构建电流互感器饱和模型的基础上,利用HYBRISIM进行了大量的仿真实验,仿真结果表明:基于改进型序阻抗原理的保护方案,较原方案在保护动作的可靠性和灵敏性等方面均有较大的改善和提高,与传统的比率制动型差动保护相配合,可构成一种较理想的变压器主保护方案.     

IEC60909短路电流计算标准分析

国际电工委员会(IEC)于2001年新制定的短路电流计算标准同我国当前普遍使用的传统算法相比,有很 大程度的变化,虽然计算项目多,但概念明确,算法简单扼要,阻抗修正具有科学性,其计算的短路电流接近发电机额 定输出时的短路电流。鉴于我国电力行业与国际接轨的必然趋势,IEC新标准被审批为我国正式的国家标准只是时 间的问题。     

轴向双分裂结构变压器阻抗计算的修正系数和分裂系数分析

通过分析和比较,得出了220kV轴向双分裂变压器的穿越阻抗、半穿越阻抗、分裂阻抗计算的修正系数和分裂系数值.     

基于改进粒子群算法的无线电能传输高频阻抗数值研究

为提升磁谐振式无线电能传输系统的传输精度和传输效率,需研究磁耦合谐振式无线电能传输过程的高频阻抗特性。依据最大功率传输原则,获取阻抗匹配适应度函数,通过适应度函数,得到匹配高频阻抗实部和虚部,从电容实时调整的角度出发,更新粒子速度和位置,混沌局部搜索最优粒子;采用惩罚函数处理越界粒子,依照最终获取的最优粒子调整无线电能传输系统中的电容,使调整后无线电能传输系统高频阻抗和适应度函数获取的高频阻抗数值一致,实现对无线电能传输系统中的高频阻抗匹配。实验分析发现,采用该方法匹配高频阻抗后,无线电能传输精度最高可达96.59%。